1. Technical Field
This disclosure relates to light emitting diodes (LEDs), dimmer controls, flyback controllers, and power factor correction.
2. Description of Related Art
Cold cathode fluorescent lamps have long-since been used in offices and have become popular in the home. Compared to incandescent lamps, their lumens per watt may be very high, saving energy. However, they may require a high voltage AC inverter and may contain toxic mercury.
Light-emitting diodes (LEDs) are also now capable of providing high light output per watt, comparable to cold cathode fluorescent lamps. Unlike cold cathode fluorescent lamps, moreover, they may not require high voltage and do not usually contain mercury.
However, the intensity of LEDs may vary as the square of changes in the voltage that is applied to them. The voltage ripple of a traditional power supply, therefore, can cause very substantial swings in the current which travels through the LEDs. The frequency of the ripple may be too high to be noticeable to the naked human eye. However, a large ripple current may decrease the efficiency of the LEDs and the purity of the color which they emit.
This ripple may be reduced by using a very large output filtering capacitance. However, very large capacitors can be costly, bulky, and prone to failure.